1. Field of the Invention
The present invention relates to an image display apparatus, and more particularly to an image display apparatus displaying a complete image frame by projecting partial images, which are provided by at least one reflection-type image display device, onto appropriate positions.
2. Description of the Related Art
DLP (Digital Light Processing) technology is being focused on as worldwide demand for digital broadcasting-related technologies and equipment increases. A DMD (Digital Micro-mirror Device), a core device of DLP technology, is a type of semiconductor optical switch with integrated micro-mirrors. A micro-mirror with a square shape, one side of which has a length in a range of 14 to 16 μm is provided on each semiconductor cell, and the micro-mirror operates by electrostatic action of the semiconductor cell disposed directly thereunder. Each micro-mirror corresponds to one pixel, and constitutes an image by adjusting a light reflection angle to express color and brightness. An operation of the DMD will be described as follows with reference to FIG. 1.
FIG. 1 is a view schematically illustrating an operation of a related DMD device. A DMD 20 includes a first micro-mirror 22 and a second micro-mirror 24 provided on a semiconductor substrate 21, and each of the micro-mirrors 22, 24 controls one pixel. The respective micro-mirrors 22, 24 can be inclined at a certain angle according to an electrical signal applied to the semiconductor substrate 21. Commercialized micro-mirrors generally have an incline angle of ±10 degrees.
The micro-mirrors 22, 24 are inclined at an angle of +10 or −10 degrees according to an on/off signal applied to the semiconductor substrate 21. As a result, the micro-mirrors 22, 24 reflect R (Red), G (Green) and B (Blue) light irradiated from a light source 10 toward a screen (not illustrated) or a light-absorbing portion 40. Here, the light-absorbing portion 40 absorbs the light reflected thereto to prevent unnecessary diffusion of light.
It should be noted from the example illustrated in FIG. 1 that a pixel 32 controlled by the first micro-mirror 22, and a pixel 34 controlled by the second micro-mirror 24 are in off and on states, respectively.
In this way, by rapidly adjusting the inclination of the respective micro-mirrors 22, 24 provided in the DMD 20, the respective pixels 32, 34 controlled by the micro-mirrors 22, 24 are repeatedly put in on-off states for light projection, so that brightness and color can be displayed.
Employment of the DMD can reduce noise or deterioration of image quality occurring when a digital signal is converted into an analog signal, and can prevent color bleeding and spotting. Also, since the distance between the micro-mirrors is very small (approximately 1 μm) the DMD is suitable for processing the high-definition and high-luminance moving image of the HD (High Definition) digital television system.
In such a DMD, since each micro-mirror controls one pixel, the quality and the resolution of a display increases as the number of micro-mirrors increases, which can be achieved by reducing the size of micro-mirrors or increasing the on-chip area of DMD.
However, there is a limitation in reducing the size of micro-mirrors, and increasing the on-chip area of a DMD is an obstacle to miniaturizing an image display apparatus. Further, when the on-chip area of the DMD increases, the yield of a micro-mirror is lowered, which is a problem.
Therefore, a technology is required that is capable of maintaining the size and the quality of an image projected by an image display apparatus when the image display apparatus is miniaturized.